[AstroPy] BCE Time & Dates?

[Derek Homeier]

Hi Rick,
> 
> I'm simulating Kepler's "Harmony of the Spheres" using the extended JPL ephemerides not usually available so that I can go back to Bischop Ussher's and Kepler's creation dates, thereby using astropy.time.Time for convenience functions.  However, although
> 
> 	>>> from astropy.time import Time
> 	>>> t = Time('4444-10-03T09:00:00')
> 	>>> str(t)
> 	'4444-10-03T09:00:00.000'
> 	>>> t.jd
> 	3344473.875
> 
> obviously works, this doesn’t:
> 
maybe the Bishop was right? ;-)

> 	>>> t = Time('-4444-10-03T09:00:00')
> 	Traceback (most recent call last):

`Time` does support a class of `long*` subformats, which are even automatically recognised,
but somewhat less than intuitive - they require a sign+5-digit year format!

 t = Time(‘-04444-10-03T09:00:00’)

should work (at least create a valid Time object. Not sure if there is a logical reason why
signed 4-digit years cannot be recognised (other than apparently only exactly two year
formats being defined; so <4 digits are not accepted either). Might be worth filing an issue.

The `datetime` overflow is a limitation of the builtin library:
datetime.MINYEAR
The smallest year number allowed in a date or datetime object. MINYEAR is 1.

so nothing you can really do about it at the Astropy level.

HTH
					Derek